Fast Zn2+ Transport in Aqueous Zinc Ion Batteries: A Composition-Activity Analysis of Prussian Blue Analogues as Positive and Hydrated Zinc Vanadate as Negative Electrode Materials.

With growing demand for safe and sustainable energy-storage systems, aqueous zinc-ion batteries (AZIBs) are emerging as promising candidates due to their non-flammable electrolytes and environmental benignity. However, their practical deployment is hindered by sluggish Zn2+ transport and electrode instability. In this work, we examine the influence of composition on Zn2+ storage in Prussian Blue Analogue (PBA) positive electrodes- Na2CuFe(CN)6·yH2O (Cu-PBA), Na2CoFe(CN)6·yH2O (Co-PBA) and the mixed-metal Na2Co0.5Cu0.5Fe(CN)6·yH2O (CoCu-PBA). Guided by theoretical calculations, CoCu-PBA exhibits the most favorable Zn2+ intercalation behavior, delivering 58 mAh g-1 at 100 mA g-1. For the negative electrode, Zn-vanadate (ZnxV2O5·yH2O, ZnVO) with its expanded ion-diffusion channels and lower band gap compared to V2O5, provides enhanced diffusion pathways and achieves 80 mAh g-1 at 100 mA g-1. A full AZIB cell assembled using CoCu-PBA and ZnVO with a ZnSO4-silica gel electrolyte delivers a specific capacity of 49 mAh g-1 (@100 mA g-1), an energy density of 61 Wh kg-1 (@125 W kg-1), a power density of 612 W kg-1 (@18 Wh kg-1) and excellent cycling stability (92% retention over 500 cycles at 300 mA g-1). These findings highlight an optimized electrode-electrolyte design for advancing high-performance AZIBs.